Federal authorities have accused a New Haven drug dealer of setting an apartment house fire that killed three people and then trying to throw off investigators by threatening witnesses against him at a federal grand jury.

Hector Natal, 26, who has used a variety of addresses in New Haven, is accused of multiple crimes in a federal indictment made public Thursday, including conspiracy to distribute narcotics, attempted arson, three counts of arson resulting in death and witness tampering.

He faces a possible life sentence.

Natal's father, Hector Morales, is accused in the same indictment of conspiring to distribute cocaine and marijuana, tampering with witnesses and destroying evidence. Morales, 50, is described in the indictment as driving his son to drug deals in the family's blue 1994 minivan.

Natal has been a target of federal law enforcement for more than a year. But it wasn't until the grand jury indictment was returned Wednesday that he was charged in the arson at 48-50 Wolcott St. early on the morning of March 9, 2011, that killed Wanda Roberson, 42, her son Quayshawn Roberson, 8, and her niece Jaquetta Roberson, 21.

Natal is accused of dousing a stairway with gasoline and lighting it, trapping the victims in the building. He also is accused in the indictment of failing in an earlier attempt to burn down the two-story residential building in October 2010.

The indictment accuses Natal of lighting the building on fire "in part as retaliation for failure to pay a drug debt."

Natal pleaded guilty in U.S. District Court to related drug offenses in October. His father was charged for the first time in the indictment, made public by federal prosecutors.

Morales was arrested Thursday. Natal, long a suspect in the three arson deaths, has been in custody for about a year.

During the week prior to the arson, the indictment accuses Natal of repeatedly telephoning someone identified in the indictment as a resident of 50 Wolcott St. Natal made the final three calls to the resident about two hours before he is accused of setting the fire, according to the indictment.

After the fire was set, the indictment said that Morales drove Natal away from the burning building.